Pneumatic hammer.



' Nu. 672,638; Patented Apr. 23, |901.

. J. DUNLOP.

PNEuMATlc HAMMER.

(Application led le`e'hr 26, 1901.)

\\\\\\\\ x my ATIOMEYG lo, 672,638. PatentedlApr. 23, |901., J. DUNLOP.

PNEUIIATIG HAMMER.

" (No Model.) (Applimim med Feb' 26'. um.) 2 Sheets-Sheet 2.

UNITED STATES PATENT QEETCE..

JAMES DUNLOP, OF MANCHESTER, ENGLAND, ASSIGNOR TO CHARLES HENRY SCHILL,OF SAME PLACE.

PNEUMATIC HAMMER.

SPECIFICATION forming part of Letters Patent N o. 672,638, dated April23, 1901.

Application med February 26, 1901. semi No. 48,951. (No model.)

This invention relates to pneumatic and like percussive hammers of thedifferentialpiston inertia-valve type, and has for its object animproved. construction of the inertiavalve and air-passages whereby theaction of the valve in distributing the compressed air or other motivefluid will be rendered` more certain and the resulting action of thehammer itself be such that very little jarring or vibration will takeplace.

Hitherto the use of inertia-valves in pneumatic and like percussivehammers has resuited in faulty and uncertain action, owing to theexcessive rebound of the valve from its terminal stops at either end ofits travel, and consequently an objectionable amount of jarring andvibration has taken place.

The means taken to prevent unnecessary or excessive rebounding of theinertia-valve and the improved construction and arrangement of partsnecessary therefor constitute the chief features of this invention.

In the accompanying drawings, Figure l is a longitudinal sectionalelevation of the improved pneu matic or like percussive hammer adaptedfor use as a hand-tool. Fig. 2 is a similar View, but showing the partsin the relative positions they occupy when the piston has reached theother end of its stroke.

In the views, A designates the barrel or cylindrical body of the hammer,and B a differential piston fitted to slide therein.` The annular spaceC formed by the difference in the two diameters of the piston B issupplied with compressed air or other motive iiuid, at such times as itis desired to work the hammer, through a passage D, drilled in the bodyA and communicating with a starting-valve E, placed in the handle F.

The handle F is secured to the body A by means of a screwed collar G,mounted loosely on the body, and when screwed up the parts are lockedtogether by teeth on a springcatch I, engaging a ring of teeth formed onthe collar G.

The compressed air or other motive i'luid is supplied to the handle Fthrough a flexible pipe (not shown) attached to the nozzle H, and thestarting-valve E is opened when required against the pressure of themotive luid by the operator depressing the triggerlever J with histhumb.

Within the piston B is drilled a valve-race K, in which is iitted with asliding fit a hollow inertia piston-valve L, having fitting parts atsuch a distance apart as to cover and uncover almost simultaneously thetwo rows of holes M and N, drilled through the smaller diameter of thepiston B. That part of the inertia-valve L which lies between thelitting parts has holes O drilled through it, and at the end of thevalve farthest awayv from the handle F a very small hole P is drilled. Aplug Q is screwed into the end of the piston B, and this plug limits thetravel of the inertia-valve L toward that end of the piston, the traveltoward the other end being limited by the opposing wall of the smallchamber R. (See Fig. l.)

On the end of the piston B is a projection S for striking any toolplaced in the tool-socket T, and between the tool-socket T and that partof the barrel A Which iits the smaller diameter of the piston B is achamber U, communicating with the atmosphere through the exhaust-portsV.

The action of the parts is as follows: The motive fluid admitted bydepressing the trigger J and opening the valve E ows through the passageD into the annular space C and pressing on the annular area of thepiston B tends t-o move it into the position shown in Fig. l. In thisposition and with the inertiavalve L in the position there shown themotive fluid will pass from the annular space C through the holes N andO to the space behind the larger end of the piston, and there, acting onits full area, will drive it into the position shown in Fig. 2, wherethe projection S is shown in contact with a tool in the tool-socket T,the blow having been delivered and the motion of the piston arrested.When the motion of the piston is thus suddenly ar- IOO rested, themomentum of the inertia-valveiL will carry it also into the positionshown in Fig. 2 or into an approximate position. In moving into thisposition the valve L will compress the motive fluid in the small chamberR to a higher pressure than that acting on thelarger'end of the pi-ston,and thus prevent the valve L fromV striking violently against theopposing wall of the chamber R, and so obviate jarring,as well asexcessive rebound of the valve, as the compressed iiuid can escapegradually through the small hole P. When the inertia-,valve Lhas movedinto the position shown in Fig. 2,' communication between the annularspace() and the space behind the larger end of the piston B is cu-t oitby the iitting part-of the valve L covering the 4holes N andcommunication between the atmosphere, and the space beh-ind the largerend of the piston is established by the other fitting part of the valveL uncovering theholes M. .The exhaust of the-motive fluid now takesplace through the holes O and M, chamber U, land, ports V. When thefluidpressure in the space behind the larger end of the piston 'B issufliciently reduced, the motive fluid, acting on the annular area ofthe piston, will again move it into the position shown in Fig. 1, andduring thatmovement the holes M in the smaller part of the piston B willpass into the. fitting part of the barrel A, and thereby communicationbetween the atmosphere and the space behind theV larger end of thepistonwill be cutoi. The motive' fluid remaining in the spacebehind thelarger end of the piston B will thenbecompressed during the remainder ofthe stroke until the pist0n is brought to a stop in the position shownin Fig. 1. Just previous to reaching that position the holes M willpassk into the annular space C and mot-ive ilui-d will flow through theholes M and O and acting on the full area of the piston B will suddenlyarrest its motion and then drive it back on the reverse stroke alreadydescribed. The motion of the piston B bein-g thus suddenly arrested themomention the valve L will cause a slight reduction of fluid-pressure inthe small chamber R, and this'prevents the valve L from strikingviolently against the plug Q and so prevents any excessive rebound. Thehammer will continue working as described so long as the thumb of theoperator remains pressing down the trigger J and motive uid continues toenter through the starting-valve E.

Having now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare thatwhat I claim is- 1. In a pneumatic or like percussive hamme-r, incombination, a barrel or cylindrical body provided with passages for thesupply of motive Huid under pressure, a differential piston'fitted toslide therein, an annular space formed by the difference'in the twodiameters of the piston, a hollow inertia piston-valve fitted inside thepiston, and having fitting parts at each end adapted to alternatelycover and uncover almost simultaneously two sets of, holesinthe smallerdiameter ofl thepiston, the said inertia-valve having a set of holesbetween its fitting ends communicating with the spacev between it andthe piston, and a single small hole in its end communicating with asmall chamber formed between the valve'and the interior of the strikingend of the piston, and an enlargedchamber with eX- haust-ports beyondthat part of the barrel which fits the smaller diameter of thepiston,

. allv arranged and operating substantially as and for the purposesherein described with reference to the drawings.

2. In a pneumatic or like percussive hammer having a barrel fitted withadifferential piston,.the combination with the inertia-valve L providedwith a small hole'P, of the chamber R andthe motive-fiuidpassages andports forming a fluid-pressure check at each end of `the traverse of theinertiavalve substantially as herein set forth.

In witness whereof'I have hereunto set my hand inpresence of twowitnesses.

JAMEs DUN-Lor.

